<template>
  <div class="pagination" style="display: flex; justify-content: center">
    <button :disabled="pageNo==1" @click="$emit('getPageNo',pageNo - 1)">上一页</button>
    <button v-if="startNumAndEndNum.start>1" @click="$emit('getPageNo',1)" :class="{active:pageNo==1}">1</button>
    <button v-if="startNumAndEndNum.start>2">···</button>
    <div v-for="(item, index) in startNumAndEndNum.end" :key="index">
      <button v-if="item >= startNumAndEndNum.start" @click="$emit('getPageNo',item)" :class="{active:pageNo==item}">
        {{ item }}
      </button>
    </div>

    <button v-if="startNumAndEndNum.end < totalPage - 1">···</button>
    <button v-if="startNumAndEndNum.end < totalPage" @click="$emit('getPageNo',totalPage)" :class="{active:pageNo==totalPage}">
      {{ totalPage }}</button>
    <button :disabled="pageNo==totalPage"  @click="$emit('getPageNo',pageNo + 1)">下一页</button>
    <!-- {{ startNumAndEndNum }} -->
    <button style="margin-left: 30px">共 {{ total }} 条</button>
  </div>
</template>

<script>
export default {
  name: "Pagination",
  //pageNo是当前页数,pageSize是每页显示的条数,total是总条数,continues是连续显示的页数,
  props: ["pageNo", "pageSize", "total", "continues"],
  computed: {
    totalPage() {
      //获取总页数
      return Math.ceil(this.total / this.pageSize);
    },
    startNumAndEndNum() {
      const { pageNo, totalPage, continues } = this;
      //定义2个变量起始数和结束数的变量
      let start = 0;
      let end = 0;
      //如果总页数没有连续页码多
      if (continues > totalPage) {
        start = 1;
        end = totalPage;
      } else {
        //正常现象
        start = pageNo - parseInt(continues / 2);
        end = pageNo + parseInt(continues / 2);
      }
      //做一个范围限制处理
      if (start < 1) {
        start = 1;
        end = continues;
      }
      if (end > totalPage) {
        end = totalPage;
        start = totalPage - continues + 1;
      }

      return { start, end };
    },
  },
};
</script>

<style lang="less" scoped>
.pagination {
  text-align: center;
  button {
    margin: 0 5px;
    background-color: #f4f4f5;
    color: #606266;
    outline: none;
    border-radius: 2px;
    padding: 0 4px;
    vertical-align: top;
    display: inline-block;
    font-size: 13px;
    min-width: 35.5px;
    height: 28px;
    line-height: 28px;
    cursor: pointer;
    box-sizing: border-box;
    text-align: center;
    border: 0;

    &[disabled] {
      color: #c0c4cc;
      cursor: not-allowed;
    }

    &.active {
      cursor: not-allowed;
      background-color: #409eff;
      color: #fff;
    }
  }
}
.active{
  background: skyblue;
}
</style>